Apparatus for energizing an audion circuit



y 17, 1932- G. B. cRousE 1,858,323

APPARATUS FOR ENERGIZING AN AUDION CIRCUIT Filed Jan. 20, 1928 Defecfor Pa wer- 771be l i/amewf i 6 '6 g 6 wmwm 6H0; may

Patented May 17, 1932 UNITED STATES GEORGE B. GROUSE, OE WOODCLIFF, NEW JERSEY, ASSIGNOR TO CONNER GROUSE COR- PORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK APPARATUS FOR ENERGIZING AN AUDION CIRCUIT Application filed January 20, 1928. Serial No. 248,250.

This invention relates to apparatus-for energizing an audion circuit, and more particularly to a filter for use between a source of rectified current and a direct current load circuit such as the circuit or circuits of an audion amplifier.

The filter network is of the same general type and has the same suppression characteristic as the filter described in my copending application Serial No. 680,096, filed December 12, 1923. 7

Anobject of the invention is to provide a simple and economical filter which will etfect the desired degree of suppression of alternating components present in a rectified current supply. An object is to provide apparatus for economically energizing audions of -different power requirements from a source of alternating current, the apparatus including circuit elements for supplying alternating current or rectified current and filtered current to the several circuits. A further object is to provide a filter network in which the impedance elements form a plurality of lVheatstone bridge circuits having arms in common. A further object is to provide a filter network includingimpedance elements for eliminating the effects of an alternating potential existing between points of the network across which there exists a direct current potential suitable for biasing the grid of a power tube. further object is to provide efiicient and economical apparatus for energizing all of the circuits of a radio receiver from a source of alternating current.

These and other objects of the invention will be apparent from the following specification, when taken with the accompanying drawmg, 1n which the smgle view is a schematic diagram of one embodiment of the.

and 8 are connected across the sections of the secondary winding for eliminating radio fre quency radiation. A condenser 9 is shunted across the leads 10 and 11 which pass the rectified pulsating direct current to the filter mesh.

The impedances of the filter mesh are arranged to form a pair of Wheatstone bridges which are energized in parallel from the rectified current leads 10, 11, one bridge net- I work supplying filtered current to the plate circuits of the audions and the other bridge supplying filtered current to the filament circuits of all audions except thepower tube which is customarily employed in the last stage of a radio receiver. The network may be, and preferably is so arranged that the bridges have two balancing arms in common. In the drawing, the resistive arms A, B, cooperate with arms G,.D to provide the bridge network across which the plate circuits are connected, and a second pair of resistive arms E, F cooperate in a similar manner'withthe arms 0, D to form the filament supply bridge. 7 The bridge arms C, each include inductive impedance, the arm C comprising an inductance 12 in series with a condenser 13, and the arm D comprising the inductance 14:, the inductances having a common core 15. Each ofthe' bridge networks may be substantially identical with the bridge type filter described in my copending application, Serial No. 247,952, filed January 19, 1928, the imjpedances-of the arms being so related that the bridges are balanced for the frequency of the most disturbing component, and the positive direct terminal taps 16, 17 of the plate and filament supply systems, respectively,

preferably being adjustable within narrow H limits to correct for manufacturing variations.

The junction 18 of the arms C, D serves as a common negative terminal for the plateand filament circuits, the maximum plate voltage being obtained by a tap to the junction of inductance 12 and capacity 13 of arm G. The lower plate voltages are supplied from terminal 16 of the bridge network, the positive lead to the plate circuits including an inductance 19011 core 20 for suppressing components of frequencies for which the bridge is not balanced, and a resistance 21 for reducing the voltage to a value suitable for the detector audion. Suitable condensers 22, 23 are connected across the plate circuits to provide a by-pass for signal currents.

In the drawing, the power supply appara tus is shown in connection with a radio receiver which includes a plurality of radio frequency amplifying audions R, an audion detector D, audio frequency amplifier A, and a power tube P. To avoid confusion, the circuit diagram of the receiver includes only those circuit elements which are directly associated with the power supply device. The filaments of all audions except the last or power tube stage are connected in series, the positive terminal +A of the filament chain being connected to the junction 17 of the arms E, F, and a resistance 24 being included in the lead from the other end of the filament chain to the common terminal A-B of the receiver. The negative terminal 18 of the plate and filament circuits of the supply device is connected to the common negative terminal of the receiver, and leads extend from the positive plate voltage taps of the filter network to the +180 terminal of the power tube plate circuit, the +90 terminal of the amplifier plate circuits, and the detector terminal of the detector plate clrcuit.

The rectifier and filter network, as so far described, supplies current to all circuits of the receiver except the grid and filament circuits of the power tube P, it being noted that the grid bias for the audio amplifier A is obtained by connecting the grid return to a point in the series filament circuit which is at a potential more negative than that of amplifier filament, i. e., to the negative end of or an intermediate point on resistance 24.

The filament of the powerstage is supplied with alternating current of appropriate voltage by the secondary winding 25 on the transformer which feeds the rectifier. A. potentiometer 26 is connected across the filament terminals and the adjustable tap 27 of the potentiometer is connected to a negative point in the series filamentcircuit of the other audions and preferably to the most negative point of that circuit. 7

To obtain the relatively high bias potential required for certain types of power tubes, advantage is taken of the direct current drop across arm D. The terminal 0 I of the receiver is connected by lead 28 to a tube.

point in inductance 14 which is so spaced from the more positive terminal 18 of the inductance that the direct current potential drop between those points will supply the desired negative bias potential for the power Since the lead 28 and terminal 18 are at different alternating current potentials, the connection 28 includes a coil 29 which is so coupled to the inductance 14 that the alternating current voltage induced in coil 29 is substantially equal in magnitude and of opposite phase to the alternating current drop across the portion of inductance 14 which is included in the grid circuit. Substantially unity coupling between coils 14 and 29 is preferably employed, coil 29 having the same number of turns as the portion of coil 14 between lead 28 and terminal 18, and beingwound in the same sense.- The effect of this back coupling is to bring the G 40 terminal to the negative direct current potential corresponding to the point of connection on coil 14, and to the alternating current potential of the point 18, i. e., the potential of point 27 in the filament circuit of the power tube P. There is, of course, a slight resistive alternating current drop, which is not compensated by this method, but such drop is so small that it may be neglected. A condenser 80 is connected between the grid end of the compensating coil 29 and terminal 18 to allow free passage of signal currents.

It is to be understood that filament, plate and grid bias voltages of any desired magnitude may be obtained by a suitable design of he transformer and filter network, and that the particular voltages indicated on the drawing are merely examples of voltages which may be appropriate for a conventional receiver. Various changes may be made in the construction and arrangement of the elements of the electrical network without departing from the spirit of my invention as set forth in the following claims. I claim:

1. In apparatus for energizing the filament and plate circuits of an audion amplifier.

from a source of rectified current, impedances providing a path across said source, and impedances of a different type cooperatin with the impedances of said path to provi e two \Vheatstone bridges having said path in common as two adjacent balancing arms thereof, and means for connecting the said filament and plate circuits across the respective bridges as arms conjugate to the said source.

2. The invention as set forth in claim 1, wherein said path comprises a pair of inductances having their outer ends connected to the respective source terminals and a capacity joining the inner ends of said inductances.

3. The invention as set forth in claim 1, wherein the said two adjacent arms formed by the said path comprise an inductance terminating at the negative terminal of said source, and a serially connected inductance and a capacity, the inductance terminating at the positive terminal of saidsource, and the remaining arms of the said two bridge networks being formed by resistances.

4. In apparatus for use between 'asource of rectified current andan audion amplifier,

a filter network including an inductance for suppressing alternating components from current supplied to the audion plate circuit, and circuit elements for applying to the audion grid a bias potential more negative than that of the cathode terminal of the audion, said circuit elements including a coil coupled magnetically to said inductance in such sense as to neutralize alternating components tending to pass to said grid.

5. In a filter network for use between a source of direct current and a plurality of audion circuits, a plurality of impedances arranged as a IVheatstone bridge across which said source and one of said audion circuits are connected as the conjugate arms thereof, the impedance forming the arm of said bridge between the negative terminals of said source and the said audion circuit comprising an inductance, means for connecting the grid return of another audion circuit to an intermediate point in said inductance, said means including as a series element thereof a coil coupled to said inductance to oppose the flow of alternating components through said means.

6. In apparatus for energizing a plate and a grid circuit from a source of rectified current, positive and negative leads for connecting said plate circuit in series with said source, an impedance in each of said leads, capacity in shunt to said impedances, a connection from one of said leads to said grid circuit, and means in said connection cooperating with one of said impedances for neutralizing the flow of alternating components through said connection to the grid.

In testimony whereof I affix my signature.

GEORGE B. CROUSE. 

